In recent years, the effective use of coal has received attention, and from now on, it is predicted that the demand for a clean coal utilization process will be increased. In order to convert coal into a high value-added energy medium, advanced technologies such as a technology of gasifying coal and a technology of refining the gasified coal are used.
In a process of refining coal gasification gas (gasification gas) made by gasifying coal, which has received attention as one of technologies to cope with such a system, as in the following reaction formula (1), a CO shift reaction in which carbon monoxide (CO) reacts with water to produce hydrogen (H2) and carbon dioxide (CO2) is applied (for example, refer to Patent Literatures 1 and 2).CO+H2O→H2+CO2  (1)
A power generation plant which applies refined gas obtained by subjecting gasification gas to the CO shift reaction as described above and refining the resultant, as gas for the turbine, and a chemical product synthesis plant which uses the refined gas as a raw material for synthesizing chemical products such as methanol and ammonia has been suggested. As the power generation plant which uses and applies the gasification gas to power generation, for example, a coal gasification combined power generation (Integrated coal Gasification Combined Cycle (IGCC)) system has been suggested (for example, refer to Patent Literatures 3 and 4). The IGCC system is referred to as a system in which coal is converted into combustible gas in a gasification furnace at a high temperature and a high pressure to produce gasification gas and the gasification gas is used as the raw material in a gas turbine and a steam turbine for combined power generation.
In order to refine the coal gasification gas and produce the refined gas, a CO shift catalyst which accelerates the reaction in which CO contained in the gasification gas is reformed and converted into CO2 (CO shift reaction) is used. The coal gasification gas is allowed to pass through a CO shift reaction apparatus having a plurality of reactors provided with CO shift catalyst layers filled with the CO shift catalyst, and the CO shift reaction as in the above formula (1) occurs in the presence of the CO shift catalyst in the reactors of the CO shift reaction apparatus, thereby producing reformed gas.
In general, in order to produce the reformed gas by the CO shift reaction in the reactor, the CO shift catalyst needs to be limited to a predetermined temperature range (for example, 250° C. to 350° C.) in which the CO shift catalyst is usable. Therefore, the CO shift reaction apparatus is provided with a plurality of groups of a reactor and a cooler and is adjusted to allow the reaction to proceed while the temperature of the CO shift catalyst is in the predetermined temperature range (250° C. to 350° C.).